1. Field of the Invention
The present invention relates to an exhaust system for a watercraft, and more particularly to a monitoring and control system for a catalytic exhaust system of a watercraft.
2. Description of Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries a rider and possibly one or two passengers. A relatively small hull of the personal watercraft commonly defines a riders"" area above an engine compartment. A two-cycle internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The jet propulsion unit is located within the tunnel and is driven by a drive shaft. The drive shaft usually extends between the engine and the jet propulsion device, through a wall of the hull tunnel.
An exhaust system of the personal watercraft discharges engine exhaust to the atmosphere either through or close to the body of water in which the watercraft is operating. Although submerged discharge of engine exhaust silences exhaust noise, environmental concerns arise. These concerns are particularly acute in connection with two-cycle engines because engine exhaust from two-cycle engines often contains lubricants and other hydrocarbons.
Such environmental concerns have raised a desire to minimize exhaustion of hydrocarbons and other exhaust byproducts (e.g., carbon monoxide and oxides of nitrogen), and thus reduce pollution of the atmosphere and the body of water in which the watercraft is operated. In response to the increased concerns regarding exhaust emissions, some personal watercraft engines recently have become equipped with a catalyst to convert exhaust byproducts to harmless gases.
Catalysts must operate at a relatively high temperature in order to produce the necessary thermal reaction and burning of the exhaust byproducts. A catalytic device thus desirably operates within a specific range of temperature so as to effectively and efficiently convert engine exhaust into generally harmless gases.
Some prior exhaust systems have employed a cooling jacket about the catalytic device to maintain the catalytic device within the desired temperature range. In some systems, at least a portion of the cooling water also is introduced into the exhaust system to not only further cool and silence the exhaust gases, but also to assist the discharge of exhaust gases. The added water to the exhaust system, however, gives rise to possible damage to the catalyst.
A need therefore exists for a system to monitor the operational conditions of the catalytic device and the exhaust system and to control an indicator panel, as well as the engine, in response to the sensed operational conditions
One aspect of the present invention involves a watercraft comprising an internal combustion engine having at least one exhaust port. An output shaft of the engine drive a propulsion device to propel the watercraft. An exhaust system includes an exhaust passage that extends between the engine exhaust port and a discharge port. A catalytic device treats exhaust gases from the engine before discharge through the discharge port, and a cooling jacket extends along a portion of the exhaust system in the vicinity of the catalytic device. An exhaust system temperature sensor is arranged to lie adjacent to at least a passage of the cooling jacket. In this position, the temperature sensor obtains accurate readings of the portion of the exhaust system which is cooled by the cooling jacket.
Another aspect of the present invention involves a watercraft comprising an internal combustion engine having at least one exhaust port. An exhaust system includes an exhaust passage that extends between the engine exhaust port and a discharge port. A cooling system includes a cooling jacket that extending along a portion of the exhaust system. A sensor is used to determine an operating characteristic of the exhaust system which is indicative of the operational condition of the cooling system and communicates this characteristic to a control system. The control system in turn operates the engine depending upon the operational condition of the cooling system.
An additional aspect of the invention involves a control method for preventing excess heat in a watercraft. The method involves sensing a characteristic of an exhaust system of the watercraft which is indicative of the operational state of a cooling system, and comparing the sensed characteristic against a first characteristic datum to determine whether the sensed characteristic falls outside the first characteristic datum. The first characteristic datum is preselected to define a first warning state. A warning indicator is activated if the sensed characteristic falls outside the first characteristic datum. The method also involves comparing the sensed characteristic against a second characteristic datum to determine whether the sensed characteristic falls outside the second characteristic datum. The second characteristic datum is preselected to define a second warning state. The speed of the engine is reduced if the sensed characteristic fall outside the second characteristic datum.
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follows.